1. Field of the Invention
This invention relates to a method of making a semiconductor film, and more particularly to a method of making a semiconductor film and a photovoltaic device for depositing a semiconductor film by plasma decomposition of a reaction gas on a non-flat surface combined with a curved or flat surface of a substrate.
2. Description of the Prior Art
A semiconductor film of an amorphous silicon system obtained by the plasma decomposition of the reaction gas has been used as photovoltaic devices, so called solar cells for directly converting solar energy to electrical energy, photoconductive drums for electronic photography or copiers, and the like. Since photovoltaic devices employ inexhaustible solar energy as an energy source, they have attracted the attention as a solution to the problem associated with exhaustion of energy resources. The sun renders the energy of about 1 kW/m.sup.2 to the ground during fine weather. When the photovoltaic device for converting such solar energy to electrical enerry is used in a home as a power source, it is generally installed on the rooftop or roof of the house.
Roofing tiles provided with solar cells, that is, tile-shaped photovoltaic devices, as disclosed in Japanese published unexamined patent application No. 57-68454 or Japanese published unexamined utility model application No. 58-11261, are suitable for home power sources.
One object of the present invention is to provide a method of making a semiconductor film for depositing a good semiconductor film on a curved surface of a substrate such as a photoconductive drum or roofing tile with solar cells suitable for the home power source.
It has been known that an amorphous silicon film is produced by a glow discharge in a silicon compound atmosphere as disclosed in Japanese published examined patent application No. 53-37718 (U.S. Pat. No. 4,064,521). The formation of the amorphous semiconductor film by using known glow discharge has such a disadvantage that since a glass or stainless steel substrate to deposit the semiconductor film is located between opposing parallel electrodes for exciting the glow discharge, the substrate is intersected with the moving direction of high speed charged particles of plasma in the moving range with the result that the high speed charged particles in the plasma impinge upon the substrate surface, thereby deteriorating characteristics of a transparent conductive film previously deposited on the substrate or the amorphous semiconductor film gradually deposited on the substrate. In addition, although the surface of the substrate to deposit the amorphous semiconductor film is flat, the substrate according to the present invention is of curved surface. Therefore, when the substrate with the curved surface is arranged between parallel flat electrodes as in the conventional technique, the distance between the curved surface and one of parallel flat electrodes becomes unequal, so that the deposited amorphous semiconductor film may not become uniform.
Accordingly, it was difficult to directly deposit uniform semiconductor film on the substrate having the non-flat surface.